There used to be a popular belief that “ontogeny recapitulates phylogeny,” meaning that the development of the embryo followed, roughly, the evolutionary history of the species. Kind of a cool thought, but not really true. Certain primative features do appear in the embryo that have been lost in the organism once born/hatched/etc (e.g. tail for humans), but there’s no real strong relationship between phylogeny and ontogeny.
As for metamorphosis, I agree there doesn’t seem to be any real scientific relationship w/ evolution, though one can certainly make metaphorical relationships out of the two processes of change. In evolution, selection acts on phenotypes, themselves determined by interactions between genotype and environment, and results in differential reproduction of individuals with different phenotypes such that genes, gene combinations, and phenotypes change over loooooong periods of time. In metamorphosis, major anatomic and physiologic changes occur in an individual as an expression of certain genes that are activated in a predetermined time and order by either internal or external cues. This process is, itself, genetically determined and subject to evolution, and I believe it is limited to invertebrates with, presumably, a less complex anatomy to re-arrange than a vertebrate.
Still, I know morgantj has the soul of an artist, and I can certainly see how the two process, resulting as they do in the develpment of radically new forms from pre-existing forms, one at the species level over long periods of time and the other at the individual level over shorter periods, have a certain poetic symmetry regardless of whether they are “really” related in a scientific sense.
There are ways in which developmental processes and evolutionary processes can interact. One of my favorites is neotany, the retention of juvenile characteristics in adulthood. Juvenile mammals tend to have a suite of characterstics such as proportionally larger and rounder heads than adults, relatively larger eyes, shorter/blunter faces, etc. These seem to trigger parenting behavior in adults. Humans have bred domestic animals, especially companion animals, to retain these features for life because we think they’re cute (think, Chihuahuas, other brachycephlic [aka snub-nosed or smushy-faced] breeds, etc). We ourselves also have a degree of neotany, and there are lots of interesting theories (probably nto really proven or even provable) that it has to do with the worm and fuzzy feelings needed for complex and successful social interactions.